When dragging a knot along a constraint line, then allow snapping the position of the mouse pointer instead of its projection onto the constraint line (for this a check box has been added to the preferences dialog)

(bzr r8523)

1 files changed, 23 insertions, 2 deletions

diff --git a/src/knot-holder-entity.cpp b/src/knot-holder-entity.cpp
index 4225dd9e3..bf7505f3c 100644
--- a/src/knot-holder-entity.cpp
+++ b/src/knot-holder-entity.cpp
@@ -91,9 +91,12 @@ KnotHolderEntity::snap_knot_position(Geom::Point const &p)
 {
     Geom::Matrix const i2d (sp_item_i2d_affine(item));
     Geom::Point s = p * i2d;
+
     SnapManager &m = desktop->namedview->snap_manager;
     m.setup(desktop, true, item);
+
     m.freeSnapReturnByRef(Inkscape::SnapPreferences::SNAPPOINT_NODE, s, Inkscape::SNAPSOURCE_HANDLE);
+
     return s * i2d.inverse();
 }
 
@@ -102,10 +105,28 @@ KnotHolderEntity::snap_knot_position_constrained(Geom::Point const &p, Inkscape:
 {
     Geom::Matrix const i2d (sp_item_i2d_affine(item));
     Geom::Point s = p * i2d;
-    Inkscape::Snapper::ConstraintLine transformed_constraint = Inkscape::Snapper::ConstraintLine(constraint.getPoint() * i2d, (constraint.getPoint() + constraint.getDirection()) * i2d - constraint.getPoint() * i2d);
+
     SnapManager &m = desktop->namedview->snap_manager;
     m.setup(desktop, true, item);
-    m.constrainedSnapReturnByRef(Inkscape::SnapPreferences::SNAPPOINT_NODE, s, Inkscape::SNAPSOURCE_HANDLE, transformed_constraint);
+
+    Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+    if ((prefs->getBool("/options/snapmousepointer/value", false))) { // legacy behavior (pre v0.47)
+        // Snapping the mouse pointer instead of the constrained position of the knot allows to snap to
+        // things which don't intersect with the constraint line. This should be handled by the
+        // smart dynamic guides which are yet to be implemented, making this behavior more clean and
+        // transparent. With the current implementation it leads to unexpected results, and it doesn't
+        // allow accurately controlling what is being snapped to.
+
+        // freeSnap() will try snapping point p. This will not take into account the constraint, which
+        // is therefore to be enforced after snap_knot_position_constrained() has finished
+        m.freeSnapReturnByRef(Inkscape::SnapPreferences::SNAPPOINT_NODE, s, Inkscape::SNAPSOURCE_HANDLE);
+    } else {
+        // constrainedSnap() will first project the point p onto the constraint line and then try to snap along that line.
+        // This way the constraint is already enforced, no need to worry about that later on
+        Inkscape::Snapper::ConstraintLine transformed_constraint = Inkscape::Snapper::ConstraintLine(constraint.getPoint() * i2d, (constraint.getPoint() + constraint.getDirection()) * i2d - constraint.getPoint() * i2d);
+        m.constrainedSnapReturnByRef(Inkscape::SnapPreferences::SNAPPOINT_NODE, s, Inkscape::SNAPSOURCE_HANDLE, transformed_constraint);
+    }
+
     return s * i2d.inverse();
 }